A simple and miniaturized sample preparation method for determination of amphetamines in urine was developed using on-column derivatization and gas chromatography-mass spectrometry (GC-MS). Urine was directly applied to the extraction column that was pre-packed with Extrelut and sodium carbonate. Amphetamine (AP) and methamphetamine (MA) in urine were adsorbed on the surface of Extrelut. AP and MA were then converted to a free base and derivatized to N-propoxycarbonyl derivatives using propylchloroformate on the column. Pentadeuterated MA was used as an internal standard. The recoveries of AP and MA from urine were 100 and 102%, respectively. The calibration curves showed linearity in the range of 0.50-50 microg/mL for AP and MA in urine. When urine samples containing two different concentrations (0.50 and 5.0 microg/mL) of AP and MA were determined, the intra-day and inter-day coefficients of variation were 1.4-7.7%. This method was applied to 14 medico-legal cases of MA intoxication. The results were compared and a good agreement was obtained with a HPLC method.